Dissertation Research: Origin and Evolution of Endemic Sideritis (Lamiaceae) from the Macaronesian Archipelagos

[801594 . Jansen]在德克萨斯大学Robert Jansen博士的指导下，研究生Janet Barber正在研究Sideritis属（Lamiaceae科）中Marrubiastrum亚属植物的起源和进化。该组包含24种多年生物种，仅在加那利群岛和马德拉群岛的马卡罗尼西亚群岛上发现。这些植物形态多样，除少数种外，一般分布在单个岛屿上。然而，作为一个群体，他们利用了两个群岛上所有不同的生态区。该亚属表现出广泛的染色体非整倍性，这是一种在多年生植物和岛屿植物中罕见的染色体数目变化类型。由于最近（1992年）对亚属的修订，该组的形态学得到了很好的理解，但物种之间的进化关系尚不清楚。有人认为，Sideritis的马卡罗内西亚成员与地中海东部地区的物种最密切相关，但没有系统发育上的支持。此外，尚不清楚岛屿分类群是来自它们的大陆亲戚，还是大陆物种可能是在大陆更新世冰川时期之后从岛屿重新引入的。本研究将利用分子标记发展该亚属的系统发育。这一推断的进化模式将表明岛屿分类群是否形成了一个有凝聚力的进化群体，这意味着单一的引入该地区。它将确定最近的大陆亲戚，并将指出迁移的方向。它还将检验马卡罗尼西亚和地中海东部之间存在生物地理联系的假设。将染色体数目以及地理和生态分布绘制到系统发育树上，将有助于解释这些因素在岛屿内亚属进化中的作用。作为第一个将分子技术应用于大西洋群岛Lamiaceae植物群的研究，这项工作将补充其他植物科的研究，这些研究已经记录了Macaronesia特有的进化模式，并将对了解其植物群的起源和进化做出重大贡献。

9801594 Jansen Under the direction of Dr. Robert Jansen at the University of Texas, graduate student Janet Barber is studying the origin and evolution of the plant subgenus Marrubiastrum in the genus Sideritis (family Lamiaceae). This group contains 24 perennial species found only in the Macaronesian archipelagos of the Canary Islands and Madeira. These plants display great variety in morphological form and, except for a few species, generally have highly restricted distributions on single islands. Yet as a group they have exploited all of the diverse ecological zones present in the two archipelagos. The subgenus exhibits extensive chromosomal aneuploidy, a type of change in chromosome number considered rare for perennial plants in general and island plants in particular. Morphology of the group is well-understood due to a recent (1992) revision of the subgenus, but evolutionary relationships among the species are not known. It has been suggested that the Macaronesian members of Sideritis are most closely related to species from the eastern Mediterranean region, but there is no phylogenetic support for this assertion. In addition, it is not known whether the island taxa are derived from their continental relatives, or if the mainland species may have been reintroduced from the islands following Pleistocene glacial episodes on the continent. The proposed study will develop a phylogeny for the subgenus using molecular markers. This inferred evolutionary schema will show whether the island taxa form a cohesive evolutionary group, implying a single introduction to the region. It will identify the closest continental relatives and will indicate the direction of migration. It will also test the hypothesis of a biogeographic link between Macaronesia and the eastern Mediterranean. Mapping of chromosome number and geographical and ecological distribution onto the phylogenetic tree will permit interpretation of the roles of these factors in the evolution of the subgenus within the islands. As the first study to apply molecular techniques to a group in the Lamiaceae of the Atlantic archipelagos, this work will complement studies in other plant families that have documented evolutionary patterns unique to Macaronesia and will make a significant contribution to understanding the origin and evolution of its flora.